1. Field of the Invention
The present invention relates to a circuit arrangement for modifying pyramidal texture coordinates for three-dimensional (3-D) graphics applications and also to a display apparatus including or being driven by such a circuit arrangement, particularly but not exclusively a stereoscopic or multiple view display apparatus.
2. Description of the Related Art
An example of such a circuit arrangement and its use in a single view (non-stereoscopic) display apparatus is described in our European patent application EP-A-0 438 195 which provides a circuit arrangement for converting pyramidal texture coordinates into corresponding physical texture memory addresses in an electronic display apparatus. The circuit arrangement comprises a pyramidal coordinate input for receiving a two-dimensional (2-D) coordinate pair and an associated level coordinate, together with means for generating from the received coordinate pair and level coordinate a corresponding physical texture memory address. The texture memory holds a pyramidal or part pyramidal array of texture element ("texel") values representing a 2-D modulation pattern (the texture) to be mapped onto surface primitives, with each level of the pyramid holding a 2-D version of the pattern filtered to a different level of resolution. Suitable filtering methods for the generation and storage of pyramidal texture arrays are described in a paper entitled "Pyramidal Parametrics" by Lance Williams, Computer Graphics, Volume 17, No 3 (July 1983) at pages 1 to 11.
EP-A-0 438 195 is concerned with an arrangement for translating texture map addressing to allow for efficient storage of part-pyramidal arrays in a linearly addressed (one-dimensional) texture memory, with a simple offset mechanism enabling rapid indexing between corresponding areas of maps of differing resolutions.
Most 3-D graphics systems can produce auxiliary information for each pixel in the rendered image, in addition to the color and intensity, such as the depth of the nearest surface impacting each pixel as is commonly available from a z-buffer. Given depth information for the nearest surface impacting each pixel, it is possible to blur the rendered image by filtering such that the amount of blurring increases as a function of the difference between the depth associated with the pixel and some programmable depth value corresponding to a point of interest. The effect mimics what happens in the cinema when a camera focuses on a point of interest and other parts of the scene are blurred. Previously, however, systems such as that of EP-A-0 438 195 have required the blurring effect to be applied as a further processing step to the rendered and texture mapped image.